Think Draconic Visage on a much larger scope, Imagine if most monsters had a "unique drop" that was some part of their corpse, was rare, and could be added to equipment for bonuses and abilities...

Unicorn Skull/Black Unicorn SkullProposed Smithing/Crafting level: 40/45Item to be augmented: Innoculation BraceEffect: Infinite Immunity to disease, and for the Black Unicorn Skull you cannot be poisoned until the poison effect you are under wears off

Jungle Snake FangsSmithing/Crafting level: 50Item to be Augmented: Green Spikey VambracesEffect: Poisons those in combat with you for 1 damage

Aquanite LightSmithing/Crafting level: 80 Item to be Augmented: Farseer Helm/Archer HelmEffect: Acts as light source, increased stat, all attackers will have prayer drain as if they had -10 prayer boost added to their current equipment boost

But... but... what's the point in such a complicated effect that will only work for pj'ing slayers who obviously didn't go prepared to slay? It's like...

*goes to cocatrices in PVP world*"Yo, take off your shield a sec!"*kills the idiot for taking off his shield - and thus completing the condition on the effect - with your added defence bonuses... wait what?*"HAHA! Now these cocatrices are mine!"

First, the scenario is stupidly complicated and in context of the scenario it's even more pointless.

Even if it's just... gives you extra defence bonuses against slayer monsters you aren't equip to fight it'd be better, but it's just silly as it is.